The first trials of mobile WiMax technology in the UK are set to begin, but service providers are not yet convinced that the technology can make the grade in the cut-throat world of mobile broadband.

Equipment maker Nortel has enlisted the help of fixed WiMax provider Urban Wimax to test its latest fourth-generation (4G) mobile WiMax technology based on the IEEE 802.16e standard. The trial will take place later this year, providing around 100 mobile device users with minimum download speeds of 1Mbit/s, with 2Mbit/s expected and up to 5Mbit/s achievable.

Nortel is conducting this trial in anticipation of Ofcom's planned auction of licences to use the 2.5/ 2.69GHz frequency spectrum in early 2008, which will give providers the bandwidth they need to offer commercial mobile broadband services.

But Gartner analyst Akshay Sharma said most carriers are still in wait-and-see mode when it comes to mobile WiMax, with chief technology officers at major telcos still saying they will believe it when they see it.

"Some frankly do not even believe it will work - they want to see it in a live production environment and go through the same rigorous trials and testing that fixed WiMax has," Sharma said.

Even if mobile WiMax proves to have the potential to be commercially viable, many observers remain uncertain about consumer and business demand for services based on yet another mobile broadband technology.

Uptake of existing 3G and HSDPA mobile broadband has been disappointing, with the high cost of per-megabyte downloads and patchy service availability considered the biggest stumbling blocks.

Amrit Heer, Nortel's European head of wireless market development, said mobile WiMax has the potential to bring that cost down. It should also be cheap for providers to deploy because of lower transmission equipment overheads, though whether providers offer regional or national coverage will depend on the licences allocated by Ofcom.

"3G is a really basic service for applications like email, which suffers from a lack of throughput, scalability and quality of service, said Heer. WiMax has three to five times more capacity and a cost per bit that is one tenth of 3G, so the cost of owning it is far lower."

Mobile WiMax will also have to compete with the Wi-Fi hotspots, which are now in place at most travel hubs. These have proved very popular with mobile workers who like the idea of being able to access wireless connectivity at a fixed cost.

Despite its involvement with the Nortel trial, even Urban Wimax might not bid for a licence to offer services in the 2.5/2.69GHz spectrum, according to chief executive Sasha Williamson. Competition from a range of fixed and mobile operators is expected to be fierce, and Urban Wimax could well find itself priced out of the bidding.

"Our collaboration with Nortel is to [show] that 4G mobile multimedia is available," said Williamson. "The objective here is to make sure we have the right ecosystem on the supply side, and the integration with the back-end systems."